drm/radeon/dp: fix lane/clock setup for dp 1.2 capable devices

Only DCE5+ asics support DP 1.2.

Noticed by ArtForz on IRC.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org

1 files changed, 15 insertions, 2 deletions

diff --git a/drivers/gpu/drm/radeon/atombios_dp.c b/drivers/gpu/drm/radeon/atombios_dp.c
index 330f8df65b09..225f6c66effa 100644
--- a/drivers/gpu/drm/radeon/atombios_dp.c
+++ b/drivers/gpu/drm/radeon/atombios_dp.c
@@ -291,6 +291,19 @@ static int dp_get_max_dp_pix_clock(int link_rate,
 
 /***** radeon specific DP functions *****/
 
+static int radeon_dp_get_max_link_rate(struct drm_connector *connector,
+                                       u8 dpcd[DP_DPCD_SIZE])
+{
+        int max_link_rate;
+
+        if (radeon_connector_is_dp12_capable(connector))
+                max_link_rate = min(drm_dp_max_link_rate(dpcd), 540000);
+        else
+                max_link_rate = min(drm_dp_max_link_rate(dpcd), 270000);
+
+        return max_link_rate;
+}
+
 /* First get the min lane# when low rate is used according to pixel clock
  * (prefer low rate), second check max lane# supported by DP panel,
  * if the max lane# < low rate lane# then use max lane# instead.
@@ -300,7 +313,7 @@ static int radeon_dp_get_dp_lane_number(struct drm_connector *connector,
                                         int pix_clock)
 {
         int bpp = convert_bpc_to_bpp(radeon_get_monitor_bpc(connector));
-        int max_link_rate = drm_dp_max_link_rate(dpcd);
+        int max_link_rate = radeon_dp_get_max_link_rate(connector, dpcd);
         int max_lane_num = drm_dp_max_lane_count(dpcd);
         int lane_num;
         int max_dp_pix_clock;
@@ -338,7 +351,7 @@ static int radeon_dp_get_dp_link_clock(struct drm_connector *connector,
                         return 540000;
         }
 
-        return drm_dp_max_link_rate(dpcd);
+        return radeon_dp_get_max_link_rate(connector, dpcd);
 }
 
 static u8 radeon_dp_encoder_service(struct radeon_device *rdev,